Risk factors associated with highly pathogenic avian influenza subtype H5N8 outbreaks on broiler duck farms in South Korea

Abstract

Highly Pathogenic Avian Influenza (HPAI) subtype H5N8 outbreaks occurred in poultry farms in South Korea in 2014 resulting in significant damage to the poultry industry. Between 2014 and 2016, the pandemic disease caused significant economic loss and social disruption. To evaluate the risk factors for HPAI infection in broiler duck farms, we conducted a retrospective case-control study on broiler duck farms. Forty-three farms with confirmed laboratories on premises were selected as the case group, and 43 HPAI-negative farms were designated as the control group. Control farms were matched based on farm location and were within a 3-km radius from the case premises. Spatial and environmental factors were characterized by site visit and plotted through a geographic information system (GIS). Univariable and multivariable logistic regression models were developed to assess possible risk factors associated with HPAI broiler duck farm infection. Four final variables were identified as risk factors in a final multivariable logistic model: "Farms with ≥7 flocks" (odds ratio [OR] = 6.99, 95% confidence interval [CI] 1.34-37.04), "Farm owner with ≥15 years of raising poultry career" (OR = 7.91, 95% CI 1.69-37.14), "Presence of any poultry farms located within 500 m of the farm" (OR = 6.30, 95% CI 1.08-36.93) and "Not using a faecal removal service" (OR = 27.78, 95% CI 3.89-198.80). This highlights that the HPAI H5N8 outbreaks in South Korea were associated with farm owner education, number of flocks and facilities and farm biosecurity. Awareness of these factors may help to reduce the spread of HPAI H5N8 across broiler duck farms in Korea during epidemics. Greater understanding of the risk factors for H5N8 may improve farm vulnerability to HPAI and other subtypes and help to establish policies to prevent re-occurrence. These findings are relevant to global prevention recommendations and intervention protocols.

Risk factors associated with Avian Influenza subtype H9 outbreaks on poultry farms in Kathmandu valley, Nepal

“…The farms that had no foot bath at entrance are almost three times more at risk of detecting AI subtype H9 compared to farms that had no foot bath at entrance. This result is consistent with the study conducted in south Korea [16].…”

“…As the farm production system becomes older, the biosecurity facilities may become older and disrupted. Also, as the farms grows older, it keeps producing many batches of poultry such that there is higher burden of virus around the poultry surroundings [16]. Also, the commercial layers were at higher risk of detecting AI subtype H9.…”

“…The risk factors for the detection of Avian Influenza were identified from literature review and expert’s opinion [16]. The risk factors selected were broadly divided into following categories: i) Farm and bird characteristics ii) Farm management and ii) Biosecurity situation of the farm.…”

Fine-scale tracking of wild waterfowl and their impact on highly pathogenic avian influenza outbreaks in the Republic of Korea, 2014–2015

“…We acknowledge that the horizontal transmission of HPAI through poultry trade networks between poultry farms was likely a significant factor in its spread, and these events were not fully captured in our study 52 . While the multiple-site production system of the modern livestock industry has significantly improved the efficiency of production, livestock movement between farms is considered an important route of disease transmission 63 – 69 .…”

“…Duck farms had approximately three times higher risk of HPAI outbreaks than chicken farms during the HPAI epidemics period. Duck farms in ROK have been more susceptible to spillover of novel HPAI strains from wild birds than chicken farms due to the lack of enhanced biosecurity facilities and practices, and the higher density of duck farms around major wintering sites of wild migratory birds compared to chicken farms 40 , 48 – 52 . Furthermore, the HPAI H5N8 strain in the ROK is considered to be more host-adapted to the order Anseriformes based on its lower mortality among, and higher transmissibility and affinity for, ducks compared to other HPAI strains 30 .…”